In the process of painting iron parts, there is often no rust after the pre-treatment of the workpiece, but rust, part of the rust occurs in the washing process after degreasing, generally easy to rust iron in the molding process will be applied on the surface of the anti-rust oil to temporarily cut off the corrosive medium, but after the pre-treatment degreasing process, The iron has lost the protection of anti-rust oil, at this time the degreaser is strongly alkaline, and it is not easy to return rust, but with step by step washing, the PH of the water on the surface of the workpiece gradually decreases close to neutral, and only a thin layer of water film on the surface of the workpiece is exposed to the air when the groove is discharged between processes or the transition section of the spray line body. More oxygen molecules will dissolve into the water film at the workpiece interface. As water is used as electrolyte, oxygen molecules will rob iron electrons, resulting in an electrochemical reaction of oxygen absorption corrosion, leading to the appearance of rust in iron materials.
Post time: Aug-11-2023